1. Field of the Invention
The present invention relates to an electronic watch, and more specifically it relates to an electronic watch having a drive motor which is driven by a normal hand-movement drive pulse and a drive motor which is driven by a non-normal hand-movement drive pulse that differs from the above-noted normal hand-movement drive pulse, so that even if the power supply voltage or drive conditions change, a proper drive condition is maintained for the drive motor which is driven by a normal hand-movement drive pulse, and which can also achieve low-power-consumption operation
2. Description of the Related Art
There is a usual type of stepping motor for an electronic watch rotates in the forward direction only in response to, for example, an input signal, and is configured so as not top rotate in the reverse direction.
For this reason, if it is desirable to cause the rotor to rotate in the reverse direction, for example to set the hand positions, it is necessary to perform drive with a special reverse drive pulse.
A disclosure of such a special reverse drive pulse was made in Japanese Unexamined Patent Publication (KOKAI) No. 52-80063, in which there is a reverse-rotation pulse in which two alternating pulses form one group, and a reverse-rotation pulse in which three alternating pulses form one group.
Of late, many solar cell watches, which have a solar cell, the light incident to which is converted to electrical energy, which is stored in a capacitor or secondary cell, this capacitor or secondary cell being used as the drive source.
In this type of solar cell watch, electrical energy is generally stored during the day and discharged during the evening, and there is a considerable variation in the voltage of the capacitor or secondary cell over even a period of one day.
Therefore, in this type of solar cell watch in particular, it is desirable that a stepping motor operates normally with as low a voltage as possible.
However, the reverse rotation operation of the above-noted stepping motor exhibits a narrower range of operating voltage than for forward operation, and it is particularly difficult to achieve normal operation at a low voltage.
Additionally, because the drive frequency for fast forward drive is high, the pulse width must be made narrow, making normal operation at a low voltage difficult.
An example of a system for hand movement in an electronic watch having a stepping motor in the past is disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 63-58192, in which the rotation and non-rotation of the rotor are detected, and when the rotor is non-rotating, load compensation is performed by outputting a compensation drive pulse, thereby causing the stepping motor to rotate reliably, and to drive, via the gear train, the second hand, minute hand, and hour hand.
The disclosure of Japanese Unexamined Patent Publication (KOKAI) No. 63-58192 will be generally explained, with reference made to FIG. 1, FIG. 2, and FIG. 3. FIG. 1 is a block diagram of a electronic watch of the past.
FIG. 2 and FIG. 3 are waveform diagrams which show the rotation detection operation of the load compensation of the electronic watch which is shown in FIG. 1, in which FIGS. 2 (a), (b), (c), and FIGS. 3 (a), (b), and (c) are approximately the same as FIGS. 4, 5, 6, 7, 8, and 9 in the Japanese Unexamined Patent Publication (KOKAI) No. 63-58192.
In FIG. 1, the normal watch section 200 corresponds to the FIG. 1 in the Japanese Unexamined Patent Publication (KOKAI) No. 63-58192, this drawing having been simplified for the purpose of the description.
In this drawing, the reference numeral 10 denotes a first stepping motor, 13 is a first rotor which is a rotor of the first stepping motor 10, 201 is an oscillator circuit, 202 is a frequency divider circuit, 203 is a normal drive pulse generation circuit, 204 is a compensation drive pulse generation circuit, 205 is a coil switching pulse generation circuit, 206 is a drive pulse supply means, 207 is a load compensation control circuit, 208 is a coil switching pulse supply means, 209 is a drive circuit, and 210 is a detection circuit.
In this same drawing, 300 is a chronograph section, 20 is a second stepping motor, 301 is a chronograph pulse generation circuit, 302 is a chronograph pulse supply means, 303 is a second drive circuit, 116 is an S switch, and 117 is an R switch.
The normal watch section 200 will be described first. The oscillator circuit 201 outputs a 32768-Hz signal, based on the oscillation of a quartz crystal. The frequency divider circuit 202 divides the frequency of this signal.
The normal drive pulse generation circuit 203 generates a normal drive pulse P1 as shown in FIG. 2 (b), based on a signal of the frequency divider circuit 202.
The normal drive pulse P1 is a 5-ms pulse which has a 1/4-ms pulse resting period in every 1 ms. The compensation drive pulse generation circuit 204 generates a compensation drive pulse pH when it is judged that the first stepping motor 10 cannot rotate, as will be described later, based on a signal of the frequency divider circuit 202.
The coil switching pulse generation circuit 205 generates the coil switching pulses Pk1 through Pk13 such as shown in FIG. 2 (d), based on a signal of the frequency divider circuit 202. The coil switching pulse Pk1 is from Pk2 are sequentially output. Each of the coil switching pulses Pk has a pulse width of 0.125 ms.
The normal drive pulse P1 which is output by the normal drive pulse generation circuit 203 is supplied to the drive circuit 209 via the drive pulse supply means 206.
Then pulses are alternately supplied to the first stepping motor 10 from the coil terminals O1 and O2, the first rotor 13 rotating, at which time the current waveforms H3 and H4, shown in FIG. 2 (a) and FIG. 3 (a), are generated.
The current waveform H3 is the waveform when the first rotor 13 could rotate, and the current waveform H4 is the waveform when the first rotor 13 could not rotate.
The current waveforms H3 and H4, as shown by the current waveforms H3a and H4a, are considerable different current waveforms from the point in time after the normal drive pulse P1 is finished being output.
The detection of rotation and non-rotation conditions is judged by detecting the difference in these current waveforms by detecting the difference in the induced voltage when the coil switching pulse Pk is applied to the drive circuit of the first stepping motor 10.
That is, as shown in FIG. 2 (d) and FIG. 3 (d), at an elapsed time of 6 ms, at which point the rotation of the first rotor 13 has not completely finished, the coil switching pulse form the coil switching pulse generation circuit 205 is applied to the drive circuit 209 via the coil switching pulse supply means 208.
It is then output to the first stepping motor 10 from the coil terminal O2.
The detection circuit 210 detects whether or not the induced voltage V1 at this time exceeds the threshold voltage Vth. The load compensation control circuit 207 receives the results of this detection, and in the case in which the induced voltage V1 does not exceed the threshold voltage Vth, the next coil switching pulse Pk2 is output from the coil terminal O2.
If the induced voltage does not exceed the threshold voltage Vth, this repeated until the coil switching pulse Pk13 is output from the coil terminal O2.
If none of the induced voltages for all the coil switching pulses Pk1 through Pk13 exceeds the threshold voltage Vth, the load compensation control circuit 207 judges that the first stepping motor 10 did not rotate, and performs controls of the drive pulse supply means 206 so as to output a compensation drive pulse which is generated by the compensation drive pulse generation circuit 204, thereby causing the first stepping motor 10 to rotate, via the drive circuit 209.
However, if one of the Pk coil switching pulses Pkn has an induced voltage Vn which exceeds the threshold voltage, the next coil switching pulse Pkn+1 is switched so as to be output not from the coil terminal O2, but rather from the coil terminal O1.
Then once again the detection is performed by the detection circuit 210 of whether or not the induced voltage of, for example, coil switching pulses Pkn+1 through Pkn+6 exceed the threshold voltage Vth.
The load compensation control circuit 207 receives the results of this detection and, if even at least one of the induced voltages Vn+1 through Vn+6 of coil switching pulse Pkn+1 to Pknt+6, exceeded the threshold voltage, the judgment is made that the first stepping motor 10 has rotated, and the load compensation control circuit 207 controls the drive pulse supply means 206 so as not to output a compensation drive pulse Ph which is generated by the compensation drive pulse generation circuit 204.
If, however, not even one of the induced voltages Vn+1 through Vn+6, exceeded the threshold voltage, the judgment is made that the first stepping motor 10 did not rotate, the output of coil switching pulses Pkn+7 and thereafter being stopped, and the load compensation control circuit 207 performing control of the drive pulse supply means 206 so that a compensation drive pulse which is generated by the compensation drive pulse Ph generation circuit 204 is output to the first stepping motor 10, thereby compensation for the delay caused by non-rotation.
The above-noted detection of rotation and non-rotation will next be described in further detail. FIG. 2 (a) shows the current waveform H3 occurring when the first stepping motor 10 rotates normally, and FIG. 2 (b) and (c) show the voltages Vo1 and Vo2 occurring at this time at coil terminals O1 and O2.
FIG. 3 (a) shows the current waveform H4 which occurs when the first stepping motor load is heavy and it could not rotate, while FIGS. 3 (b) and (c) show the voltages Vo1 and Vo2 occurring at this time at coil terminals O1 and O2.
The detection of rotation of the first stepping motor 10 in FIG. 2 will next be described. As shown in FIG. 3 (b), after a normal drive pulse P1 is applied to the coil terminal O1, the coil switching pulse Pk1 is applied to the coil terminal O2 at the detection time T1, the detection circuit 210 detecting whether or not the induced voltage V1 at that time exceeds the threshold voltage Vth.
If at this time the current waveform H3 shown at FIG. 2 (a) is above the reference line G, the induced voltage V1 exceeds the threshold voltage Vth, but if it is below the reference line G, the induced voltage does not exceed the threshold voltage Vth.
The position of the current waveform H3 at the detection time t1 is d1, and because this is below the reference line G, the induced voltage V1 does not exceed the threshold voltage Vth. However, at detection time t2, the current waveform H3 is at the position d2, which is above the reference line G, this indicating that the induced voltage V2 exceeds the threshold voltage Vth.
When the coil switching voltage Pkn is applied to the coil terminal O2, if the induced voltage Vn exceeds the threshold voltage Vth, the next coil switching pulse Pkn+1 is switched so as to be applied not to the coil terminal O2, but rather to coil terminal O1. In this case, the coil switching pulses are applied to the coil terminal O1 starting with the coil switching pulse Pk3 output at the detection time t3.
In this case, in contrast to the case in which the coil switching pulse is applied to the coil terminal O2, if the current waveform H3 shown at FIG. 2 (a) is below the reference line G, the induced voltage V3 exceeds the threshold voltage Vth, whereas if the current waveform H3 is above the reference line G, the induced voltage does not exceed the threshold voltage Vth.
At the detection time t3, the coil switching pulse Pk3 is output from the coil terminal O1, and because the position of the current waveform at that time is d3, which is above the reference line G, the induced voltage V3 does not exceed the threshold voltage Vth.
Further, at the detection times t4 and t5 as well, the current waveform H3 is at the positions, d4 and d5, respectively, these both being above the reference line G, indicating that the induced voltages V4 and V5 do not exceed the threshold voltage Vth.
However, at the next detection time, t6, the current waveform H3 is at the position d6, which is below the reference line G, thereby indicating that the induced voltage V6 exceeds the threshold voltage Vth. At the six coil switching pulses Pk3 through Pk8 which are applied to the coil terminal O1, if even one of the induced voltages V3-V8 exceeds the threshold voltage Vth, the judgment is made that the first stepping motor 10 rotated.
In this case, because the induced voltage V6 exceeds the threshold voltage, the judgment is made that the first stepping motor rotated, so that the detection at coil switching pulses Pk7 and thereafter is stopped, and the compensation drive pulse Ph is not output.
Next, referring to FIG. 3, the rotation detection when the first stepping motor 10 did not rotate will be described. In this case, because the phase is 180 deg. different from the case of FIG. 2, a normal drive pulse P1 is applied to the coil terminal O2 as shown at FIG. 3 (b).
Then, the coil switching pulse Pk1 is applied to the coil terminal O2 at the detection time t1, detection being made as to whether or not the induced voltage V1 at that time exceeds the threshold voltage Vth.
In this case, similar to the case of FIG. 2 (a), if the current waveform H4 shown in FIG. 3 (a) is above the reference line G, the induced voltage V1 exceeds the threshold voltage Vth, and if it is below the reference line G, the induced voltage V1 does not exceed the threshold voltage Vth.
The position of the current waveform H4 at the detection time t1 is d1, which is below the reference line G, indicating that the induced voltage V1 does not exceed the threshold voltage Vth. Further, at the detection times t2 and t3, the current waveform H4 positions are d2 and d3, respectively, these both being below the reference line G, indicating that the induced voltages V2 and v3 do not exceed the threshold voltage Vth.
Then at the next detection time t4, the current waveform H4 position is d4, which is above the reference line G, indicating that the induced voltage V4 exceeds the threshold voltage Vth.
With the coil switching pulse Pk applied to the coil terminal O1, if the induced voltage at that time exceeds the threshold voltage Vth, the next coil switching pulse Pkn+1 is switched so as to be applied not to the coil terminal O1 but rather to the coil terminal O2. In this case, the coil switching pulses starting with the coil switching pulse at the detection time t5 will be applied to the coil terminal O2.
In this case, in contrast to the case in which the coil switching pulses are applied to the coil terminal O1, if the current waveform H4 is below the reference line G in FIG. 3 (a) the induced voltage V5 exceeds the threshold voltage Vth, and if it is above the reference line G the induced voltage V5 doe snot exceed the threshold voltage Vth.
The position of the current waveform H4 at the detection time t5 is d5, which is above the reference line G, thereby indicating that the induced voltage V5 does not exceed the threshold voltage Vth. Further at the detection times t6 through t10 as well, the current waveform H4 is at the positions d6 through d10, respectively, these all being above the reference line G, indicating that the induced voltages V6 through V10 do not exceed the threshold voltage Vth.
The coil switching pulse Pk which is applied to the coil terminal O2 is controlled by a counter, so that if during a prescribed period of time ( in this case the period between detection times t5 to t10) there is not even one time of where the threshold voltage is exceeded, detection is stopped, a judgment is made that the first stepping motor did not rotate, 32 ms after which a compensation drive pulse Ph is output to perform compensation drive of the first stepping motor 10. By doing this, the non-rotation condition is detected and load compensation operation is performed so as to output a compensation drive pulse only in the case in which it is required.
In recent years, multifunction electronic watches have appeared which have, for example, a chronograph function (abbreviated as chronograph function hereinafter) in addition to the normal time display. FIG. 4 shows a plan view of an electronic watch module of the past having a chronograph function, this electronic watch applying as well to the present invention.
In this drawing, the reference number 10 is the first stepping motor which is shown in FIG. 1, this comprising a first coil 11, a first yoke 12, and a first rotor 13. The reference numeral 20 is the second stepping motor which is shown in FIG. 1, this comprising a second coil 21, a second yoke 22, and a second rotor 23. The numeral 4 denotes a time gear train, 5 is a second hand, 6 is a chronograph gear train, 7 is a functional hand including a chronograph hand, 116 is an S used to start and stop the function including chronograph function, and 117 is an R switch used to reset function, for example, the function, for example, and chronograph function.
The first stepping motor 10 rotates the first rotor 13, 180 deg. every one second, thereby driving the second hand 5 via the time gear train, and further driving the hour hand, and the minute hand (not shown in the drawing) to perform a normal display of the time.
the second stepping motor 20 performs a chronograph operation by means of the S switch 116, rotating the second rotor 23 by 180 deg. in each 10 ms by means of a high-speed 100-Hz pulse, thereby driving the chronograph hand 7 via the chronograph gear train 6 to perform a functional display including chronograph display.
Next, the chronograph circuit operation will be described, with reference being made to FIG. 1 and FIG. 5. Since the normal watch section 200 in FIG. 1 has already been described, this description will focus on the chronograph section 300. FIG. 5 shows the pulse waveforms output by an electronic watch of the past.
A chronograph pulse generation circuit 301 generates the chronograph pulse P11 as shown at FIG. 5 (b), based on a signal from the frequency divider circuit 202. The chronograph pulse P11 is supplied from a chronograph pulse supply means 302 to a second drive circuit 303 by means of a start operation of the S switch 116, output being made alternately from coil terminal O3 and O4 of the second drive circuit 303, thereby driving the second stepping motor 20.
The normal drive pulse P1 which is applied to the coil terminal O1 of the above-noted first stepping motor 10 is a 5-ms pulse such as shown at FIG. 5 (a), this having a 1/4-ms resting period each 1 ms. Rotation and non-rotation are detected by the earlier-described method, and in the case of non-rotation, as shown at FIG. 5 (a), a compensation drive pulse Ph with a pulse width of 10 ms is output after 32 ms.
After one second, a normal drive pulse P1 is applied to the other coil terminal O2, this being alternately repeated. Next, the pulse which is applied to the second stepping motor 20 will be described. With regard to the pulse which is applied to the second stepping motor 20, as shown in FIG. 5 (b), at the point at which the S switch is operated to start the chronograph function a chronograph pulse P11 having a pulse width of 4 ms is output from the coil terminal O3 of the second coil 21.
Then, after 10 ms, the chronograph pulse P11 is applied other coil terminal O4. These outputs are alternately repeated each 10 ms.
Although the above-noted first stepping motor 10 and the second stepping motor 20 should be designed so as to be distant from one another to avoid interaction between their magnetic fields, because of a reduction in module size and the associated design requirements, there are cases in which the first stepping motor 10 and the second stepping motor 20 are disposed as shown in FIG. 4, with just a small space D between them.
Thus, when one stepping motor rotates, it magnetically interferes with the other stepping motor. In a motor such as the first stepping motor, in which detection is made of rotation and non-rotation, the above-noted magnetic interference can result in a misjudgment that the first stepping motor has rotated, when in fact it has not rotated, thereby resulting in inhibiting of the output of the compensation drive pulse, this resulting in a disturbance of the timekeeping by the watch.
In particular in the case of a stepping motor such as the second stepping motor which is rotating at a high speed of 1 Hz or higher, because pulses are constantly being output, the influence this motor drive has on the first stepping motor 10 is unavoidable. The mechanism of this erroneous detection will be described below.
FIG. 6 shows the waveforms which illustrate the rotation and non-rotation detection in the load compensation operation of the past. FIG. 6 (a) the current waveform when a normal drive pulse P2 is applied form the coil terminal O2 of the first stepping motor 10 for the case in which the first stepping motor 10 could not rotate. The solid line waveform H1 is the current waveform when there is magnetic interference from the second stepping motor 20 (that is, when the chronograph is operating), while the dotted line wave form H2 is the current waveform when there is no magnetic interference therefrom (that is, when the chronograph is not operating).
FIG. 6 (b) shows the current waveform of the second stepping motor 20 at that time. FIG. 6 (c) and FIG. 6 (d) show the voltage Vo2 at the coil terminal O2 of the first stepping motor 10 and the voltage Vo1 at the coil terminal O1 of the first stepping motor 10, respectively.
FIG. 6 (e) shows the waveforms of the coil switching pulses Pk1 through Pk13.
The current waveform of the first stepping motor 10 is a waveform such as shown as H2 in FIG. 6 (a) as long as the second stepping motor 20 is not being driven. However, if the second stepping motor 20 is being driven, it creates magnetic interference as shown in FIG. 6 (b), this resulting in the current waveform such as shown as H1 in FIG. 6 (a).
Turning now to what happens if detection of rotation and non-rotation is performed under these conditions, first a normal drive pulse P1 is output from the coil terminal O2.
Then the coil switching pulse Pk1 is applied at the coil terminal O1 at the detection time t1 and detection is made of whether or not the induced voltage V1 at that time exceeds the threshold voltage Vth. If at this time the waveform H1 is above the reference line G, the induced voltage V1 exceeds the threshold voltage, but if it is below the reference line G, it does not exceed the threshold voltage Vth.
The position of the current waveform H1 at the detection time t1 is d1, which is below the reference line G, indicating that the induced voltage V1 does not exceed the threshold voltage Vth. Additionally at detection times t2 and t3 the current waveform H1 is at the positions d2 and d3, which are both below the reference line G, indicating that the induced voltages V2 and V3 do not exceed the threshold voltage Vth. At the next detection time t4, the current waveform H1 position is d4, which is above the reference line G, thereby indicating that the induced voltage V4 exceeds the threshold voltage Vth.
With the coil switching pulse Pkn applied to the coil terminal O1, if the induced voltage at this time exceeds the threshold voltage Vth, the next coil switching pulse Pkn+1 is switch so as to be applied not to the coil terminal O1, but rather to the coil terminal O2. That is, the coil switching pulses Pk5 starting from the coil switching pulse Pk5 at detection time t5 are applied to the coil terminal O2.
In this case, in contrast to the case in which coil switching pulses are applied to the coil terminal O1, if the current waveform is below the reference line G, the induced voltage at that time exceeds the threshold voltage Vth, but if the current waveform is above the reference line G, the induced voltage does not exceed the threshold voltage Vth.
With regard to the coil switching pulse Pk5 which is now applied to the coil terminal O2 at the detection time t5, because of the influence of magnetic interference, the current waveform position H1 is d5, whereas it should normally have been at d'5. For this reason, although without the magnetic interference the position of the current waveform H2 would have been above the reference line G at d'5, indicating that the induced voltage V5 did not exceed the threshold voltage Vth, the effect of the magnetic interference is to move the position of the current waveform H1 at the d5, which is below the reference line G, indicating that the induced voltage V5 exceeds the threshold voltage Vth.
If the any one of the induced voltages V5 through V10 for the coil switching pulses Pk5 through Pk10 exceeds the threshold voltage Vth, the judgment is made that the stepping motor was driven.
Thus, although the first stepping motor has not actually rotated, an erroneous detection to the effect that it did not rotate occurs, and a compensation drive pulse Ph is not output as a result. Therefore, the action of the above-noted compensation drive pulse Ph in compensating the first stepping motor does not occur, and the time kept by this motor lags.
In addition, in the past there has been a commercially produced electronic watch which used a solar cell on the clock face, this being used in combination with a storage means such as an electrical double-layer capacitor or the like, rather than a battery (this electronic watch being referred to hereinafter as a solar watch).
Because the output voltage of an electrical double-layer capacitor is not constant, the stepping motor drive method in the solar watch was that of making a plurality of normal pulses available, these having differing driving forces. Additionally a means for detecting rotation and non-rotation was provided, a normal drive pulse being selected and output from the plurality of normal drive pulses which would enable drive with the minimum current a the voltage present at that time, thereby driving the stepping motor in a manner that accommodated the varying voltage.
The solar watch of the past will be described, with reference being made to FIG. 7. FIG. 7 shows the block diagram of the solar watch of the past, and FIG. 8 shows the waveforms of the normal pulse Ps of the solar watch which is shown in FIG. 7. In FIG. 7, the reference numeral 45 denotes a solar cell which generates electricity in response to light, 70 is an electrical double-layer capacitor which stores electrical energy, 10 is a first stepping motor, 150 is a watch circuit which operates by the electrical power which is stored in the electrical double-layer capacitor 70, 101 is an oscillator circuit which generates the reference clock required for circuit operation, 102 is a frequency divider circuit which divides the frequency of the reference clock generated by the oscillator circuit 101, 103 is a first normal pulse generation circuit which generates the normal pulses Ps1 through Ps8 for the purpose of normal drive of the first stepping motor 10 and a compensation drive pulse Psh for the purpose of performing compensating drive, 108 is a first normal pulse selection circuit which selects one moral pulse Ps from the normal pulses Ps1 through Ps8 which are generated by the first normal pulse generation circuit, 133 is a clock control circuit which performs timekeeping based on a signal from the frequency dividing circuit 102, 120 is a first drive circuit for the purpose of driving the first stepping motor 10, 115 is a second hand control circuit which is controlled by the clock control circuit 122, and which supplies the normal pulse signal Ps which is selected by the first normal pulse selection circuit 108 to the first drive circuit 120 each one second, 119 is a first detection circuit which detects the rotation and non-rotation of the first stepping motor, and 114 is a first load compensation control circuit which performs control of the first normal pulse selection circuit 108 based on the results of the judgment made by the first detection circuit 119.
Next, circuit operation will be described.
The electrical energy generated by the solar cell 45 is stored in the electrical double-layer capacitor 70. The watch circuit 150 uses the electrical double-layer capacitor 70 as its power supply, and is driven by the power supply voltage Vc.
The first normal pulse generation circuit 103 generates the normal pulses Ps1 through Ps8 and the compensation pulse Psh, based on a signal from the frequency divider circuit 102. The first normal pulse selection circuit 108 is controlled by the first load compensation control circuit 114, selects one normal pulse Ps from the normal pulses Ps1 through Ps8, according to a method to be described later, supplying this to the second hand control circuit 115 and transfers the magnitude of the currently selected normal pulse Ps to the first load compensation control circuit 114 by means of the signal S.
The second hand control circuit 115 supplies the normal pulse Ps to the first drive circuit 120 each one second, in accordance with the time that is kept by the watch control circuit 133. The first drive circuit 120 drives the first stepping motor 10 by means of the normal pulse Ps. The first load compensation control circuit 114 controls the first normal pulse selection circuit 108 by means of the results of the judgment of the first detection circuit 119, and in the case in which rotation as detected, outputs the same normal pulse Ps next time, but in the case in which non-rotation is detected, outputs the compensation drive pulse Psh and switches the next normal pulse Ps to the next larger normal pulse Ps.
Next, the pulse shapes will be described, FIGS. 8 (a) through (c) shows the waveforms of the normal pulses Ps1, Ps4, and Ps8 of the normal pulses Ps1 through Ps8 which are available. The normal pulses Ps1 through Ps8 have a pulse width of 4 ms, but each have a pulse resting period that differs by 0.05 ms each. The normal pulse Ps1, as shown in FIG. 8 (a), has a pulse resting period Ks1 of 0.35 ms every 1 ms, the normal pulse Ps4 has a pulse resting period Ks4 of 0.2 ms every 1 ms, and the normal pulse Ps8 has no pulse resting period.
Although it is not shown in the drawing, the normal pulses Ps2, Ps3, Ps5, Ps6, and Ps7 have pulse resting periods of 0.3 ms, 0.25 ms, 0.15 ms, 0.1 ms and 0.05 ms, respective, every 1 ms. FIG. 8 (d) shows the compensation drive pulse Psh which is output when the judgment is made that drive was not possible by the normal pulse Ps.
The compensation drive pulse Psh is output 32 ms after the normal pulse Ps, has a pulse width of 12 ms and has 0.5-ms pulse resting periods every 1 ms in the latter 6 ms of this 12 ms.
TABLE 1 ______________________________________ Normal Pulse Ps Pulse Resting Periods and Minimum Drive Voltages Normal Pulse Pulse Resting Period Minimum Drive Voltage ______________________________________ Ps1 0.35 ms 2.6 VPs2 0.3 ms 2.3 VPs3 0.25 ms 2.0 VPs4 0.2 ms 1.8 VPs5 0.15 ms 1.6 VPs6 0.1 ms 1.4 VPs7 0.05 ms 1.2 VPs9 (None) 1.0 V ______________________________________
As described above, because the normal pulses Ps1 through Ps8 have mutually differing pulse resting periods, the associated minimum voltage, that is, the minimum drive voltage is different for each. Table 1 shows the pulse resting periods and minimum drive voltages for each of the normal pulses Ps.
Because the normal pulse Ps8 has no resting period, it has the largest driving capacity, so that drive is possible even if Vc is only 1.0 V. The normal pulse Ps 1 has a long resting period of 0.35 ms, and thus has the smallest driving capacity. Thus, at a low voltage at which drive is not possible, drive is only possible at a power supply voltage Vc of 2.6 V or greater.
However, at a high power supply voltage Vc, the normal pulse Ps8 has more drive capacity than is necessary, so that the power consumption becomes large. In contrast to this, the normal pulse Ps1 enables drive at a power supply voltage Vc of 2.6 V or greater with a power consumption that is lower than any of the normal pulses Ps2 through Ps8. The normal pulses Ps2 through Ps7 each have the minimum drive voltages corresponding to their respective pulse resting periods. The solar watch is driven by the most optimal normal pulse Ps that has a low power consumption with respect to the power supply voltage of the electrical double-layer capacitor 70.
Next, the method of selecting an optimal normal pulse Ps will be described. In the load compensation control method practiced in the past, a given normal pulse Ps(n) is output, and if drive was not possible the next output normal pulse is selected as the next larger normal pulse Ps(n+1). If rotation occurred, however, the next pulse is the same normal pulse Ps(n), this being output a prescribed number of times, for example 100 times continuously, after which the next pulse was the next smaller normal pulse Ps(n-1).
By performing the above-noted operation, it is possible to select the optimum normal pulse. Take, for example, the case in which the power supply voltage Vc of 1.7 V, and in which the normal pulse Ps3 is output. From Table 1, it can be seen that, with a power supply voltage Vc of 1.7, the smallest normal pulse usable for drive is the normal pulse Ps5, with which drive is possible with a minimum voltage of 1.6 V, making the normal pulse Ps5 the optimum pulse when the power supply voltage Vc is 1.7 V.
Since the minimum drive voltage with the normal pulse Ps3 pulse is 2.0 V, drive is not possible with a power supply voltage Vc of 1.7 V. Thus, the first stepping motor 10 cannot be rotated, and the first detection circuit 119 makes the judgment that rotation was not possible. In accordance with the results of this judgment, the first load compensation control circuit 114 controls the first normal pulse selection circuit 108 so as to output a compensation drive pulse Psh, and also makes a switch to the next larger normal pulse Ps4 starting at the next time.
Thus, the first stepping motor 10 drive is compensated reliably by the compensation drive pulse Psh, and the next larger normal pulse Ps1 is output the next time. Note, however, that from Table 1 it can be seen that because the minimum drive voltage with the normal pulse Ps4 is 1.8 V, it still is not possible to perform drive with the power supply voltage Vc of 1.7 V. Therefore, it is not possible for the first stepping motor 10 to rotate, and the first detection circuit 119 makes the judgment that rotation was not possible.
In accordance with the results of this judgment, the first load compensation control circuit 114 controls the first normal pulse selection circuit so as to output a compensation pulse Psh and also makes a switch to the next larger normal pulse Ps5 starting the next time. Thus, the drive of the first stepping motor 10 is reliably compensated once again, and the next larger normal pulse Ps5 is output the next time. With the normal pulse Ps5 the minimum drive voltage is 1.6, so drive is possible with the power supply voltage Vc of 1.7 V.
Therefore, the first detection circuit 119 makes the judgment that rotation was possible. In accordance with the results of this judgment, the first load compensation control circuit 114 controls the first normal pulse selection circuit 108 so that a compensation drive pulse Psh is not output, and outputs the same normal pulse Ps5 the next time as well. Thus, the normal pulse Ps5 is output the next time as the normal pulse Ps. Furthermore, if the power supply voltage Vc continues to be 1.7 V, when the normal pulse Ps5 is output continuously for 100 times, the first load compensation control circuit 114 controls the first normal pulse selection circuit 108 so as to output the next smaller normal pulse Ps4 as the next normal pulse Ps.
However, because with the normal pulse Ps4 drive is not possible with the power supply voltage Vc of 1.7 V, the compensation pulse Psh is output to perform compensation drive, the normal pulse being returned to the next larger normal pulse Ps5 the next time output is made. In the above-described manner, with a power supply voltage Vc of 1.7 only one time out of 100 times is the normal pulse Ps4 output and drive not possible, so that the compensation pulse Psh is output to perform drive compensation, and at the other times drive continues with the optimum normal pulse Ps5. Although the current consumption of the compensation pulse Psh is larger than with a normal pulse Ps, this occurs only one time in 100, so that the effect extremely small and not enough to cause a problem.
Next, the case in which the power supply voltage Vc increases from 1.7 V to 2.1 V will be described. From Table 1, with a power supply voltage of 2.1 V, the optimum normal pulse Ps is the normal pulse Ps3, which has a minimum drive voltage of 2.0 V, the drive capacity with the normal pulse Ps5 being excessively large, so that the current consumption becomes larger than necessary. Note that, as described above, out of each 100 outputs of the normal pulse Ps5, the normal pulse Ps4 is output one time.
The minimum drive voltage with the normal pulse Ps4 is 1.8 V and while drive was not possible with a power supply voltage Vc of 1.7 V, drive is possible at a power supply voltage Vc of 2.1 V. Thus, when the normal pulse Ps4 is output, if the power supply voltage Vc is 2.1 V, the first stepping motor 10 is driven by this normal pulse Ps4, and the first detection circuit 119 makes the judgment that rotation was possible.
In accordance with the results of this judgment, the first load compensation control circuit 114 controls the first normal pulse selection circuit 108 so that a compensation pulse Psh is not output, and so that the same normal pulse Ps4 is selected for output next time as well. Then, the next time as well, the normal pulse Ps4 is output as the normal pulse Ps.
In addition, when the normal pulse Ps4 is output 100 times, the first load compensation circuit 114 controls the first normal pulse selection circuit 108 so that the next smaller normal pulse Ps3 is selected for output the next time. Because the minimum drive voltage with the normal pulse Ps3 is 2.0 V, so that drive is possible with a power supply voltage Vc of 2.1 V as well, the next time the same normal pulse Ps3 is output the next time as well.
By performing the above-noted operation, the normal pulse Ps3, which is the optimum normal pulse when the power supply voltage Vc is 2.1 V, is selected and output. Furthermore, after the normal pulse Ps3 is output 100 times, the next smaller normal pulse Ps2 is output, but drive is not possible at a power supply voltage Vc of 2.1 with this normal pulse Ps2, so that after the compensation pulse Psh performs compensation drive, the output normal pulse Ps is returned once again to the normal pulse Ps3. By doing this, it is possible to select and output the normal pulse which is optimum for a varying power supply voltage Vc.
This operation operates not only with respect to the power supply voltage variations, but with respect to the drive load of the calendar and the like, enabling the selection of the output of the optimum normal pulse at all times. The above-noted operation will be referred to hereinafter as multistage load compensation operation.
In recent years there has arisen demands from electronic watches for not only the normal time display, but for various additional functions such as an alarm function and a chronograph function. Specially, in the case of an analog-indicating electronic watch, there is a desire to be able to do such things as switch from the normal time display to the alarm time display, and to perform operations such as fast-forward and fast-reverse with the chronograph display, which require drive capability by means of a non-normal pulse, and these desires have occurred with solar watches as well.
However, it is known that with a solar watch the power supply voltage varies widely, making it impossible to obtain sufficient motor drive energy with a fixed pulse width when performing non-normal pulse drive such as high-speed pulse drive and reverse pulse drive at low voltages, another associated problem being that at high voltages rotor overrun occurs, preventing proper drive, and thereby limiting the voltage range over which drive is possible. Accommodation of the above-noted functions in solar watches, in which the power supply voltage varies widely, is therefore not possible.
An effective drive means when the voltage is varying is the above-described multistage load compensation operation, and it can be envisioned that this method can be used to perform high-speed rotation and reverse rotation. However, with multistage load compensation, because of the time period for detection an the time period of output of a compensation drive pulse, the amount of time until the output of the next pulse becomes long, this posing the problem of preventing high-speed drive. For example, even if the pulse width of the normal pulse is as short as 4 ms, there is an addition detection time period of approximately 20 ms, and if rotation was not possible a compensation drive pulse having a width of 12 ms is output from the 32 ms point.
Therefore, during the amount of time until the drive is completed with a compensation drive pulse, that is, during the 50-ms period of time which is the total of the 32 ms before output of the compensation drive pulse, the 12-ms pulse width of the compensation drive pulse, and the stabilization time of approximately 8 ms, it is not possible to output the next normal pulse.
Therefore, with multistage load compensation, it is not possible to perform drive with a pulse interval of smaller than 50 ms. That is, drive at a frequency of higher than 20 Hz is not possible. Thus, in solar watches in the past it was difficult to perform high-speed rotation or reverse rotation. One method of solving the above-described problem is to detect the power supply voltage, and to output high-speed pulse or reverse pulse having a width responsive to the voltage at that time. An example of detecting the voltage and changing the width of a reversing pulse was proposed as an electronic watch stepping motor in the Japanese Unexamined Patent Application S55-59375.
However when performing high-speed rotation or reverse rotation in a solar watch, in which the voltage varies over a wide ranges such as from approximately 1 V to 3 V, it is necessary to perform a plurality of voltage detections corresponding to the drive voltage ranges for these pulses. For example, if a high-speed pulse or reversing pulse is to be output to correspond to each of the dour divided voltage ranges of 1 to 1.3 V, 1.3 to 1.7 V, 1.7 to 2.3 V, and 2.3 to 3 V, it is necessary to perform voltage detection at the five voltages of 1 V, 1.3 V, 1.7 V, 2.3 V, and 3 V.
Furthermore, if the variations between components being used and environmental conditions such as the operating temperature are considered, reliable operation requires that the voltage detection be performed with considerable accuracy. It is extremely difficult to perform high-accuracy voltage detection within such as small system as an electronic watch.